Power over fiber system

ABSTRACT

A power over fiber system includes a power sourcing equipment, a powered device, an optical fiber cable, a measurer and a control device. The power sourcing equipment includes a semiconductor laser that oscillates with electric power, thereby outputting feed light. The powered device includes a photoelectric conversion element that converts the feed light into electric power. The optical fiber cable transmits the feed light from the power sourcing equipment to the powered device. The measurer measures a distance from the power sourcing equipment to the powered device. The control device controls the power sourcing equipment to output the feed light by changing a laser wavelength thereof for the distance from the power sourcing equipment to the powered device measured by the measurer.

The present application is a continuation of U.S. patent applicationSer. No. 17/442,599 filed on Sep. 23, 2021, which is a National StageEntry of PCT/JP2020/037075 filed on Sep. 30, 2020 and claims the benefitof priority from the prior Japanese Patent Application No. 2019-191756,filed on Oct. 21, 2019, the entire contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to a power over fiber system.

BACKGROUND ART

Recently, there has been studied an optical power supply system thatconverts electric power into light (called feed light), transmits thefeed light, converts the feed light into electric energy, and uses theelectric energy as electric power.

There is disclosed in Patent Literature 1 an optical communicationdevice that includes: an optical transmitter that transmits signal lightmodulated with an electric signal and feed light for supplying electricpower; an optical fiber including a core that transmits the signallight, a first cladding that is formed around the core, has a refractiveindex lower than that of the core, and transmits the feed light, and asecond cladding that is formed around the first cladding, and has arefractive index lower than that of the first cladding; and an opticalreceiver that operates with electric power obtained by converting thefeed light transmitted through the first cladding of the optical fiber,and converts the signal light transmitted through the core of theoptical fiber into the electric signal.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2010-135989 A

SUMMARY OF INVENTION Problem to Solve

In optical power supply, further improvement of optical power supplyefficiency is required. As one way therefor, improvement ofphotoelectric conversion efficiency at the power supplying side and thepower receiving side is required.

Solution to Problem

A power over fiber system according to an aspect of the presentdisclosure includes:

a power sourcing equipment including a semiconductor laser thatoscillates with electric power, thereby outputting feed light;

a powered device including a photoelectric conversion element thatconverts the feed light into electric power;

an optical fiber cable that transmits the feed light from the powersourcing equipment to the powered device;

a measurer that measures a distance from the power sourcing equipment tothe powered device; and

a control device that controls the power sourcing equipment to outputthe feed light by changing a laser wavelength thereof for the distancefrom the power sourcing equipment to the powered device measured by themeasurer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a power over fiber system according to afirst embodiment of the present disclosure.

FIG. 2 is a block diagram of a power over fiber system according to asecond embodiment of the present disclosure.

FIG. 3 is a block diagram of the power over fiber system according tothe second embodiment of the present disclosure and shows opticalconnectors and so forth.

FIG. 4 is a block diagram of a power over fiber system according toanother embodiment of the present disclosure.

FIG. 5 is a block diagram of a first configuration example in which thepower over fiber system according to the first embodiment of the presentdisclosure has components that perform power supply according totransmission length.

FIG. 6 is a line graph showing a relationship between loss at atransmission destination and the transmission length(loss-to-transmission-length characteristic) about laser wavelengths offeed light.

FIG. 7 is a block diagram of a second configuration example in which thepower over fiber system according to the first embodiment of the presentdisclosure has components that perform power supply according to thetransmission length.

FIG. 8 is a block diagram of a third configuration example in which thepower over fiber system according to the second embodiment of thepresent disclosure has components that perform power supply according tothe transmission length.

FIG. 9 is a block diagram of a fourth configuration example in which thepower over fiber system according to the second embodiment of thepresent disclosure has components that perform power supply according tothe transmission length.

FIG. 10 is a block diagram showing another configuration example of apower sourcing equipment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings.

(1) Outline of System

First Embodiment

As shown in FIG. 1 , a power over fiber (PoF) system 1A of thisembodiment includes a power sourcing equipment (PSE) 110, an opticalfiber cable 200A and a powered device (PD) 310.

In the present disclosure, a power sourcing equipment converts electricpower into optical energy and supplies (sources) the optical energy, anda powered device receives (draws) the supplied optical energy andconverts the optical energy into electric power.

The power sourcing equipment 110 includes a semiconductor laser 111 forpower supply.

The optical fiber cable 200A includes an optical fiber 250A that forms atransmission path of feed light.

The powered device 310 includes a photoelectric conversion element 311.

The power sourcing equipment 110 is connected to a power source, andelectrically drives the semiconductor laser 111 and so forth.

The semiconductor laser 111 oscillates with the electric power from thepower source, thereby outputting feed light 112.

The optical fiber cable 200A has one end 201A connectable to the powersourcing equipment 110 and the other end 202A connectable to the powereddevice 310 to transmit the feed light 112.

The feed light 112 from the power sourcing equipment 110 is input to theone end 201A of the optical fiber cable 200A, propagates through theoptical fiber 250A, and is output from the other end 202A of the opticalfiber cable 200A to the powered device 310.

The photoelectric conversion element 311 converts the feed light 112transmitted through the optical fiber cable 200A into electric power.The electric power obtained by the conversion of the feed light 112 bythe photoelectric conversion element 311 is driving power needed in thepowered device 310. The powered device 310 is capable of outputting, foran external device(s), the electric power obtained by the conversion ofthe feed light 112 by the photoelectric conversion element 311.

Semiconductor materials of semiconductor regions of the semiconductorlaser 111 and the photoelectric conversion element 311 aresemiconductors having a laser wavelength being a short wavelength of 500nm or less. The semiconductor regions exhibit light-electricityconversion effect.

Semiconductors having a laser wavelength being a short wavelength have alarge band gap and a high photoelectric conversion efficiency, and henceimprove photoelectric conversion efficiency at the power supplying sideand the power receiving side in optical power supply, and improveoptical power supply efficiency.

Hence, as the semiconductor materials, laser media having a laserwavelength (base wave) of 200 nm to 500 nm may be used. Examples thereofinclude diamond, gallium oxide, aluminum nitride and gallium nitride.

Further, as the semiconductor materials, semiconductors having a bandgap of 2.4 eV or greater are used.

For example, laser media having a band gap of 2.4 eV to 6.2 eV may beused. Examples thereof include diamond, gallium oxide, aluminum nitrideand gallium nitride.

Laser light (laser beams) having a longer wavelength tends to have ahigher transmission efficiency, whereas laser light having a shorterwavelength tends to have a higher photoelectric conversion efficiency.Hence, when laser light is transmitted for a long distance, laser mediahaving a laser wavelength (base wave) of greater than 500 nm may be usedas the semiconductor materials, whereas when the photoelectricconversion efficiency is given priority, laser media having a laserwavelength (base wave) of less than 200 nm may be used as thesemiconductor materials.

Any of these semiconductor materials may be used in one of thesemiconductor laser 111 and the photoelectric conversion element 311.This improves the photoelectric conversion efficiency at either thepower supplying side or the power receiving side, and improves theoptical power supply efficiency.

Second Embodiment

As shown in FIG. 2 , a power over fiber (PoF) system 1 of thisembodiment includes an optical power supply system through an opticalfiber and an optical communication system therethrough, and includes: afirst data communication device 100 including a power sourcing equipment(PSE) 110; an optical fiber cable 200; and a second data communicationdevice 300 including a powered device (PD) 310.

In the following description, as a general rule, components donated bythe same reference signs as those of already-described components arethe same as the already-described components unless otherwise stated.

The power sourcing equipment 110 includes a semiconductor laser 111 forpower supply. The first data communication device 100 includes, inaddition to the power sourcing equipment 110, a transmitter 120 and areceiver 130 for data communication. The first data communication device100 corresponds to a data terminal equipment (DTE), a repeater or thelike. The transmitter 120 includes a semiconductor laser 121 for signalsand a modulator 122. The receiver 130 includes a photodiode 131 forsignals.

The optical fiber cable 200 includes an optical fiber 250 including: acore 210 that forms a transmission path of signal light (signal beams);and a cladding 220 that is arranged so as to surround the core 210 andforms a transmission path of feed light (feed beams).

The powered device 310 includes a photoelectric conversion element 311.The second data communication device 300 includes, in addition to thepowered device 310, a transmitter 320, a receiver 330 and a dataprocessing unit 340. The second data communication device 300corresponds to a power end station or the like. The transmitter 320includes a semiconductor laser 321 for signals and a modulator 322. Thereceiver 330 includes a photodiode 331 for signals. The data processingunit 340 processes received signals. The second data communicationdevice 300 is a node in a communication network. The second datacommunication device 300 may be a node that communicates with anothernode.

The first data communication device 100 is connected to a power source,and electrically drives the semiconductor laser 111, the semiconductorlaser 121, the modulator 122, the photodiode 131 and so forth. The firstdata communication device 100 is a node in a communication network. Thefirst data communication device 100 may be a node that communicates withanother node.

The semiconductor laser 111 oscillates with the electric power from thepower source, thereby outputting feed light 112.

The photoelectric conversion element 311 converts the feed light 112transmitted through the optical fiber cable 200 into electric power. Theelectric power obtained by the conversion of the feed light 112 by thephotoelectric conversion element 311 is driving power needed in thesecond data communication device 300, for example, driving power for thetransmitter 320, the receiver 330 and the data processing unit 340. Thesecond data communication device 300 may be capable of outputting, foran external device(s), the electric power obtained by the conversion ofthe feed light 112 by the photoelectric conversion element 311.

The modulator 122 of the transmitter 120 modulates laser light 123output by the semiconductor laser 121 to signal light 125 on the basisof transmission data 124, and outputs the signal light 125.

The photodiode 331 of the receiver 330 demodulates the signal light 125transmitted through the optical fiber cable 200 to an electric signal,and outputs the electric signal to the data processing unit 340. Thedata processing unit 340 transmits data of the electric signal to anode, and also receives data from the node and outputs the data to themodulator 322 as transmission data 324.

The modulator 322 of the transmitter 320 modulates laser light 323output by the semiconductor laser 321 to signal light 325 on the basisof the transmission data 324, and outputs the signal light 325.

The photodiode 131 of the receiver 130 demodulates the signal light 325transmitted through the optical fiber cable 200 to an electric signal,and outputs the electric signal. Data of the electric signal istransmitted to a node, whereas data from the node is the transmissiondata 124.

The feed light 112 and the signal light 125 from the first datacommunication device 100 are input to one end 201 of the optical fibercable 200, propagate through the cladding 220 and the core 210,respectively, and are output from the other end 202 of the optical fibercable 200 to the second data communication device 300.

The signal light 325 from the second data communication device 300 isinput to the other end 202 of the optical fiber cable 200, propagatesthrough the core 210, and is output from the one end 201 of the opticalfiber cable 200 to the first data communication device 100.

As shown in FIG. 3 , the first data communication device 100 includes alight input/output part 140 and an optical connector 141 attached to thelight input/output part 140, and the second data communication device300 includes a light input/output part 350 and an optical connector 351attached to the light input/output part 350. An optical connector 230provided at the one end 201 of the optical fiber cable 200 is connectedto the optical connector 141, and an optical connector 240 provided atthe other end 202 of the optical fiber cable 200 is connected to theoptical connector 351. The light input/output part 140 guides the feedlight 112 to the cladding 220, guides the signal light 125 to the core210, and guides the signal light 325 to the receiver 130. The lightinput/output part 350 guides the feed light 112 to the powered device310, guides the signal light 125 to the receiver 330, and guides thesignal light 325 to the core 210.

As described above, the optical fiber cable 200 has the one end 201connectable to the first data communication device 100 and the other end202 connectable to the second data communication device 300 to transmitthe feed light 112. In this embodiment, the optical fiber cable 200transmits the signal light 125/325 bidirectionally.

As the semiconductor materials of the semiconductor regions, whichexhibit the light-electricity conversion effect, of the semiconductorlaser 111 and the photoelectric conversion element 311, any of thosedescribed in the first embodiment can be used, thereby achieving a highoptical power supply efficiency.

Like an optical fiber cable 200B of a power over fiber system 1B shownin FIG. 4 , an optical fiber 260 that transmits signal light and anoptical fiber 270 that transmits feed light may be provided separately.Further, the optical fiber cable 200B may be composed of a plurality ofoptical fiber cables.

(2) Components that Perform Power Supply According to TransmissionLength

[First Configuration Example to Perform Power Supply According toTransmission Length]

Next, a first configuration example to perform power supply according tothe transmission length will be described with reference to thedrawings.

FIG. 5 shows the first configuration example in which theabove-described power over fiber system 1A has components that performpower supply according to the transmission length. FIG. 6 is a linegraph showing a relationship between loss at a transmission destinationand the transmission length (loss-to-transmission-lengthcharacteristics) about laser wavelengths of feed light (feed beams).

In the following description, as a general rule, components donated bythe same reference signs as those of already-described components arethe same as the already-described components unless otherwise stated.

In FIG. 6 , loss includes both transmission loss of an optical fibercable and loss due to the photoelectric conversion efficiency. Referencesigns λ1 to λ4 in FIG. 6 represent laser wavelengths, and the wavelengthlengths satisfy “λ1<λ2<λ3<λ4”.

According to the feed beams having these different laser wavelengths,the increase rate of loss tends to be lower as the laser wavelength islonger, and the photoelectric conversion rate tends to be higher (theloss at a length of 0 tends to be smaller) as the laser wavelength isshorter.

The transmission efficiency of feed light is mainly determined from thetransmission loss and the photoelectric conversion efficiency. Hence,the laser wavelength of feed light having a high transmission efficiencydiffers from transmission length to transmission length. In the light ofthis, the power over fiber system 1A of the first configuration exampleincludes, as components that perform power supply according to thetransmission length, the power sourcing equipment 110 capable ofoutputting the feed light 112 by changing the laser wavelength thereof,a measurer 150A that measures the distance from the power sourcingequipment 110 to the powered device 310, and a control device 153A thaton the basis of the distance from the power sourcing equipment 110 tothe powered device 310 measured by the measurer 150A, controls the powersourcing equipment 110 to output the feed light 112 with a proper laserwavelength.

The power sourcing equipment 110 includes a plurality of semiconductorlasers 111A to 111N having different laser wavelengths and an opticalcoupler 113 that guides the feed light 112 output from each of thesemiconductor lasers 111A to 111N to the optical fiber cable 200A.

In FIG. 5 , for convenience in drawing, transmission lengths from therespective semiconductor lasers 111A to 111N to the optical fiber cable200A, or 200, are shown differently. However, in reality, thetransmission lengths from the respective semiconductor lasers 111A to111N to the optical fiber cable 200A, or 200, are adjusted to be equal(which applies to FIG. 7 to FIG. 9 described below).

In the first embodiment, the condition(s) for a preferred semiconductormaterial of the semiconductor laser 111 is described. At least one ofthe semiconductor lasers 111A to 111N satisfies the same condition asthe semiconductor laser 111. All the semiconductor lasers 111A to 111Nmay satisfy the condition for a preferred semiconductor material.

The laser wavelengths of the semiconductor lasers 111A to 111N are alldifferent from one another. Although it is preferable that manysemiconductor lasers be provided, at least two types thereof areprovided.

The power over fiber system 1A of the first configuration exampleincludes a separator 151A that is provided between the optical fibercable 200A and the power sourcing equipment 110 and takes out reflectedlight 112R of the feed light 112 reflected at/by the end (end face) ofthe optical fiber cable 200A close to the powered device 310, aphotodiode 152A that receives the reflected light 112R taken out by theseparator 151A, and a control device 153A that controls the powersourcing equipment 110 on the basis of detection by the photodiode 152A.

The separator 151A is configured by a beam splitter, an optical coupleror the like, and arranged between the optical coupler 113 and theoptical fiber cable 200A.

The separator 151A lets the feed light 112 pass through, the feed light112 travelling from the optical coupler 113 toward the optical fibercable 200A, and also transmits, to the photodiode 152A, a portion of thereflected light 112R travelling from the optical fiber cable 200A towardthe optical coupler 113.

The separator 151A may be provided in the middle of the optical fibercable 200A, near the end thereof close to the power sourcing equipment110.

The photodiode 152A is arranged so as to face a direction in which theseparator 151A reflects the reflected light 112R, and detects the lightintensity of the incident reflected light 112R. The detection signal ofthe photodiode 152A is input to the control device 153A.

When the distance from the power sourcing equipment 110 to the powereddevice 310 is measured, the control device 153A outputs single-pulsefeed light 112 from one of the semiconductor lasers 111A to 111N, whichare for power supply, and measures the time elapsed before thephotodiode 152A detects the reflected light 112R. From the measuredelapsed time, the control device 153A calculates the distance from thepower sourcing equipment 110 to the powered device 310. The single-pulsefeed light 112 may be output by any of the semiconductor lasers 111A to111N, which is, for example, preset.

To be precise, the control device 153A having the function ofcalculating the above distance, the separator 151A and the photodiode152A constitute a measurer 150A.

The control device 153A includes a memory that stores table data inwhich for each of groups into which transmission lengths are classified,a semiconductor laser having the highest transmission efficiency amongthe semiconductor lasers 111A to 111N is recorded. Referring to thistable data, the control device 153A selects a semiconductor laser havingthe highest transmission efficiency from among the semiconductor lasers111A to 111N on the basis of the group to which the measured distancefrom the power sourcing equipment 110 to the powered device 310 belongs.

The control device 153A makes a switch to the semiconductor laserselected from among the semiconductor lasers 111A to 111N to output thefeed light 112 thereafter.

The control device 153A may be configured by a microcomputer or asequencer using an analog circuit or a digital circuit.

The distance from the power sourcing equipment 110 to the powered device310 is measured at the start of power supply (immediately before thestart included) or at the startup of the power over fiber system 1A(immediately before the startup included).

As described above, in the power over fiber system 1A of the firstconfiguration example, it is possible that the control device 153Acontrols the power sourcing equipment to output the feed light 112 bychanging the laser wavelength thereof for the distance from the powersourcing equipment 110 to the powered device 310 measured by themeasurer 150A. This enables power supply with a laser wavelength havinga high transmission efficiency and can improve the feed light rate, ascompared with the case where power supply is performed with a fixedlaser wavelength.

The power sourcing equipment 110 has the semiconductor lasers 111A to111N having different laser wavelengths, and the control device 153Acontrols the power sourcing equipment 110 to output the feed light 112by selecting one of the semiconductor lasers 111A to 111N for themeasured distance. This enables power supply with a wide variety oflaser wavelengths without an optical element(s), such as a wavelengthconversion element.

[Second Configuration Example to Perform Power Supply According toTransmission Length]

Next, a second configuration example to perform power supply accordingto the transmission length will be described with reference to thedrawings. FIG. 7 shows the second configuration example in which theabove-described power over fiber system 1A has components that performpower supply according to the transmission length.

In the second configuration example, as shown in FIG. 7 , to the powerover fiber system 1A of the first configuration example, a reflectingdevice 361A and a control device 363A for the reflecting device 361A areadded. The reflecting device 361A has a mirror 362A that reflects thefeed light 112, and is arranged between the optical fiber cable 200A andthe powered device 310.

The second configuration example is the same as the first configurationexample except that the distance is measured on the basis of not thereflected light 112R of the feed light 112 reflected at the end face ofthe optical fiber cable 200A close to the powered device 310 but thereflected light 112R reflected by the mirror 362A.

The reflecting device 361A includes an actuator that switches the mirror362A between a reflective position where the mirror 362A can reflect thefeed light 112 and a standby position where the mirror 362A does notblock the feed light 112 from entering the photoelectric conversionelement 311, between the optical fiber cable 200A and the powered device310.

The control device 363A is configured by a microcomputer, a sequencerusing an analog circuit or a digital circuit, or the like, and controlsthe above position switching operation of the mirror 362A of thereflecting device 361A.

As the initial position, the reflecting device 361A holds the mirror362A at the standby position. When the feed light 112 is input from thepower sourcing equipment 110 to the photoelectric conversion element 311at the start of power supply or at the startup of the system, a powersource is supplied to the control device 363A.

When the power source is supplied, the control device 363A performscontrol to temporarily switch the positon of the mirror 362A of thereflecting device 361A to the reflective position and then return themirror 362A to the standby position.

This allows the control device 153A to obtain the distance from thepower sourcing equipment 110 to the powered device 310 by measuring thetime elapsed since start of output of the feed light 112 to receipt ofthe reflected light 112R reflected by the mirror 362A. This elapsed timeincludes a delay time from when the photoelectric conversion element 311receives the feed light 112 to when the control device 363A switches theposition of the mirror from the standby position to the reflectiveposition. This delay time is obtained in advance by measuring or thelike, and stored in the control device 153A. The control device 153Acalculates the distance after subtracting the delay time from theelapsed time.

The control device 153A selects a semiconductor laser having the highesttransmission efficiency from among the semiconductor lasers 111A to111N, and makes a switch to the selected semiconductor laser to outputthe feed light 112 thereafter.

With no control device 363A provided, the control device 153A may beconnected to the reflecting device 361A by another system (e.g. a signalline, etc.) different from the feed light 112 so as to be able tocontrol the reflecting device 361A.

The second configuration example can obtain the same effects as thefirst configuration example, and also, if the measurer 150A isconfigured to measure the distance from the power sourcing equipment 110to the powered device 310 by making use of reflection of the feed light112, which is laser light, with the mirror 362A, can use the reflectedlight 112R having a higher light intensity, and accordingly can measurethe distance more stably with higher accuracy.

In the first and second configuration examples, the power over fibersystem 1A is the base structure. However, the power over fiber system 1can also be configured, like the first configuration example, to performpower supply with a proper laser wavelength by providing the measurer150A and the control device 153A. The power over fiber system can alsobe configured, like the second configuration example, to reflect thefeed light 112 with the mirror 362A by adding the reflecting device 361Aand the control device 363A.

[Third Configuration Example to Perform Power Supply According toTransmission Length]

Next, a third configuration example to perform power supply according tothe transmission length will be described with reference to thedrawings.

FIG. 8 shows the third configuration example in which theabove-described power over fiber system 1 has components that performpower supply according to the transmission length.

The power over fiber system 1 of the third configuration example uses,in order to perform power supply according to the transmission length,not the reflected light 112R of the feed light 112 but reflected light125R of the signal light 125, which is laser light, reflected at the endface of the optical fiber cable 200 close to the second datacommunication device 300 (powered device 310).

In the power over fiber system 1, the first data communication device100 having the power sourcing equipment 110 includes the photodiode 131that receives the signal light 325 from the semiconductor laser 321,and, using this as a measurer, measures the distance by receiving thereflected light 125R of the signal light 125.

Further, to the power over fiber system 1, a control device 154 isadded. The control device 154 controls the transmitter 120 and the powersourcing equipment 110.

When the distance from the first data communication device 100 (powersourcing equipment 110) to the second data communication device 300(powered device 310) is measured, the control device 154 outputssingle-pulse signal light 125 from the semiconductor laser 121 of thetransmitter 120, and measures the time elapsed before the photodiode 131detects the reflected light 125R. From the measured elapsed time, thecontrol device 154 calculates the distance from the power sourcingequipment 110 to the powered device 310.

The control device 154 having the function of calculating the abovedistance, the semiconductor laser 121 and the photodiode 131 constitutea measurer.

The control device 154 too includes a memory that stores table data inwhich for each of groups into which transmission lengths are classified,a semiconductor laser having the highest transmission efficiency amongthe semiconductor lasers 111A to 111N is recorded. Referring to thistable data, the control device 154 selects, from among the semiconductorlasers 111A to 111N, a semiconductor laser having the highest electricpower transmission efficiency for the measured and obtained distancefrom the first data communication device 100 (power sourcing equipment110) to the second data communication device 300 (powered device 310) toperform power supply therewith.

The control device 154 may also be configured by a microcomputer or asequencer using an analog circuit or a digital circuit.

The distance is measured at the start of power supply (immediatelybefore the start included) or at the startup of the power over fibersystem 1 (immediately before the startup included).

The power over fiber system 1 of the third configuration example selectsone of the semiconductor lasers 111A to 111N on the basis of themeasured distance, and hence can perform power supply with a highelectric power transmission efficiency.

Further, since the photodiode 131 that receives the reflected light 125Rof the signal light 125 measures the distance, it is unnecessary toprovide the separator 151A on the route of the feed light 112. This cankeep the transmission efficiency of the feed light 112 high.

Further, since the photodiode 131, which is a fundamental component ofthe power over fiber system 1, is utilized, the number of components tobe newly added can be reduced. This can reduce the number of componentsand reduce production costs accordingly.

[Fourth Configuration Example to Perform Power Supply According toTransmission Length]

Next, a fourth configuration example to perform power supply accordingto the transmission length will be described with reference to thedrawings.

FIG. 9 shows the fourth configuration example in which theabove-described power over fiber system 1 has components that performpower supply according to the transmission length.

In the power over fiber system 1 of the fourth configuration example, ameasurer measures the distance from the first data communication device100 (power sourcing equipment 110) to the second data communicationdevice 300 (powered device 310) on the basis of the signal light (laserlight) 125 emitted from the semiconductor laser 121 provided as a laserlight source in the first data communication device 100 (power sourcingequipment 110) and the signal light (laser light) 325 as a response fromthe semiconductor laser 321 provided as a laser light source in thesecond data communication device 300 (powered device 310).

Further, to the power over fiber system 1, a control device 155 isadded. The control device 155 controls the transmitter 120 and the powersourcing equipment 110.

When the distance from the first data communication device 100 (powersourcing equipment 110) to the second data communication device 300(powered device 310) is measured, the control device 155 controls themodulator 122 of the transmitter 120 to cause the semiconductor laser121 to output the signal light 125 for distance measurement.

In the second data communication device 300, when the photodiode 331receives the signal light 125 for distance measurement, the dataprocessing unit 340 controls the modulator 322 to cause thesemiconductor laser 321 to output the signal light 325 as a response.

In order that the signal light 125 from the semiconductor laser 121 canbe identified as the signal light 125 for distance measurement, it ispreferable that, in the first data communication device 100, themodulator 122 perform unique modulation.

Similarly, in order that the signal light 325 from the semiconductorlaser 321 can be identified as the signal light 325 as a response, it ispreferable that, in the second data communication device 300, themodulator 322 perform unique modulation.

The control device 155 measures the time elapsed before the photodiode131 detects the signal light 325. From the measured elapsed time, thecontrol device 155 calculates the distance from the power sourcingequipment 110 to the powered device 310. This elapsed time includes adelay time from when the second data communication device 300 receivesthe signal light 125 to when the second data communication device 300outputs the signal light 325. This delay time is obtained in advance bymeasuring or the like, and stored in the control device 155.

This allows the control device 155 to calculate the distance from thefirst data communication device 100 (power sourcing equipment 110) tothe second data communication device 300 (powered device 310) from thetransmission speed of light after subtracting the delay time from theelapsed time.

The control device 155 having the function of calculating the abovedistance, the semiconductor laser 121, the modulator 122, the photodiode131, the semiconductor laser 321, the modulator 322, the photodiode 331and the data processing unit 340 constitute the measurer.

Like the control device 154 described above, the control device 155 tooincludes a memory that stores table data in which for each of groupsinto which transmission lengths are classified, a semiconductor laserhaving the highest transmission efficiency among the semiconductorlasers 111A to 111N is recorded. Referring to this table data, thecontrol device 155 selects, from among the semiconductor lasers 111A to111N, a semiconductor laser having the highest transmission efficiencyfor the measured and obtained distance from the first data communicationdevice 100 (power sourcing equipment 110) to the second datacommunication device 300 (powered device 310) to perform power supplytherewith.

The control device 155 may also be configured by a microcomputer or asequencer using an analog circuit or a digital circuit.

The distance is measured at the start of power supply (immediatelybefore the start included) or at the startup of the power over fibersystem 1 (immediately before the startup included). It is preferablethat the distance be measured at least in a state in which a powersource for the second data communication device 300 is secured by thefeed light 112.

The fourth configuration example can obtain the same effects as thethird configuration example, and also, since the distance is measured onthe basis of the signal light 125 emitted from the semiconductor laser121 and the signal light 325 as a response from the semiconductor laser321, can use the signal light 125, 325 having a higher light intensity,and accordingly can measure the distance more stably with higheraccuracy.

[Another Example of Power Sourcing Equipment]

FIG. 10 is a block diagram showing another configuration example of thepower sourcing equipment 110. The power sourcing equipment 110 of thisanother configuration example can be used in place of the power sourcingequipment 110 described in the first to fourth configuration examples.

Unlike the power sourcing equipment 110 having the semiconductor lasers111A to 111N having different laser wavelengths shown in the first tofourth configuration examples, this power sourcing equipment 110 has onesemiconductor laser 111. This semiconductor laser 111 satisfies thecondition for a preferred semiconductor material described in the firstembodiment.

Further, the power sourcing equipment 110 includes a plurality ofoptical elements 115A to 115N that change the laser wavelength of thefeed light 112 output from the semiconductor laser 111 to wavelengthsdifferent from one another, an optical switch 114 that guides the feedlight 112 from the semiconductor laser 111 to one of the opticalelements 115A to 115N, and an optical coupler 116 that guides the feedlight 112 having passed through any of the optical elements 115A to 115Nto the optical fiber cable 200 or 200A.

The optical elements 115A to 115N, the optical switch 114 and theoptical coupler 116 constitute a converter that converts the feed light112 of the semiconductor laser 111 into laser wavelengths different fromone another.

As each of the optical elements 115A to 115N, phosphor is used, forexample. Phosphor has a physical property of absorbing light having aspecific wavelength and emitting light having a wavelength differentfrom that of the absorbed light. The phosphor may be either transmissiveor reflective.

As each of the optical elements 115A to 115N, another component thatperforms wavelength conversion, such as an optical device capable ofconverting, by using a diffraction grating(s), the wavelength of laserlight to be reflected, may be used.

Also, as each of the optical elements 115A to 115N, nonlinear crystal(BBO crystal, LBO crystal, BiBO crystal, etc.) may be used. Nonlinearcrystal is capable of shortening the laser wavelength of the feed light112.

At least two of the optical elements 115A to 115N are provided, but itis preferable that a larger number of optical elements be prepared toconvert the laser wavelength of the feed light 112 into a wider varietyof laser wavelengths.

In FIG. 10 , for convenience in drawing, transmission lengths from therespective optical elements 115A to 115N to the optical fiber cable 200or 200A are shown differently. However, in reality, the transmissionlengths from the respective optical elements 115A to 115N to the opticalfiber cable 200 or 200A are adjusted to be equal.

The power sourcing equipment 110 shown in FIG. 10 is provided with thecontrol device 153A. The control device 153A controls the optical switch114 to select one of the optical elements 115A to 115N for the laserwavelength selected by measuring the distance.

If the power sourcing equipment 110 shown in FIG. 10 is applied to thepower over fiber system 1 of the third configuration example, thecontrol device 154 performs the selection from the optical elements 115Ato 115N, whereas if the power sourcing equipment 110 shown in FIG. 10 isapplied to the power over fiber system 1 of the fourth configurationexample, the control device 155 performs the selection from the opticalelements 115A to 115N.

Thus, if the power sourcing equipment 110 is configured to output thefeed light 112 with a laser wavelength having a high electric powertransmission efficiency by using the converter, which converts the feedlight 112 of the semiconductor laser 111 into laser wavelengthsdifferent from one another, a required number of semiconductor lasersfor power supply can be reduced.

Further, if each of the optical elements 115A to 115N that convert thelaser wavelength of the feed light 112 is an element that does not needto be controlled, such as phosphor, the number of components in thepower sourcing equipment 110 to be controlled can be reduced, and thecontrol system can be simplified accordingly.

[Others]

Although some embodiments of the present disclosure have been describedabove, these embodiments are made for purposes of illustration andexample only. The present invention can be carried out in various otherforms, and each component may be omitted, replaced or modified/changedwithin a range not departing from the scope of the present invention.

For example, FIG. 5 to FIG. 10 show examples in which the componentsthat perform power supply according to the transmission length areapplied to the power over fiber system 1 or 1A, but in the same manner,the components that perform power supply according to the transmissionlength are also applicable to the power over fiber system 1B.

INDUSTRIAL APPLICABILITY

A power over fiber system according to the present invention hasindustrial applicability to a power over fiber system that performspower supply by changing the laser wavelength.

The invention claimed is:
 1. A power sourcing equipment for supplyingpower to a powered device, the power sourcing equipment comprising: afirst semiconductor laser; a second semiconductor laser; and at leastone controller configured to estimate a distance from the power sourcingequipment to the powered device based on at least one process, selectone of the first semiconductor laser and the second semiconductor laserbased on the distance, and cause the selected one of the firstsemiconductor laser and the second semiconductor laser to output a feedlight to the powered device.
 2. The power sourcing equipment accordingto claim 1, wherein the first semiconductor laser is configured tooutput the feed light having a first laser wavelength, and wherein thesecond semiconductor laser is configured to output the feed light havinga second laser wavelength that is different from the first laserwavelength.
 3. The power sourcing equipment according to claim 2,wherein the first laser wavelength is 500 nm or less.
 4. The powersourcing equipment according to claim 2, wherein the first laserwavelength is in a range of 200-500 nm.
 5. A power sourcing equipmentfor supplying power to a powered device, the power sourcing equipmentcomprising: a semiconductor laser configured to output a feed light tothe powered device; a first laser wavelength converter configured tochange a laser wavelength of the feed light to a first laser wavelength;a second laser wavelength converter configured to change the laserwavelength of the feed light to a second laser wavelength different fromthe first laser wavelength; and at least one controller configured toestimate a distance from the power sourcing equipment to the powereddevice based on at least one process, select one of the first laserwavelength converter and the second laser wavelength converter based onthe distance, and cause the selected one of the first laser wavelengthconverter and the second laser wavelength converter to change the laserwavelength of the feed light.